Throughout the specification, reference will be made to plasma arc spray and detonation gun (D-Gun) techniques for depositing coating compositions. Typical deposition gun techniques are disclosed in U.S. Pat. Nos. 2,714,563 and 2,950,867. Plasma arc spray techniques are disclosed in U.S. Pat. Nos. 2,858,411 and 3,016,447. Other similar thermal spray techniques are known and include, for example, so-called "high velocity" plasma and "hypersonic" combustion spray processes.
U.S. Pat. No. 4,173,685 issued to M. H. Weatherly on Nov. 6, 1979, entitled "Coating Material and Method of Applying Same for Producing Wear and Corrosion Resistant Coated Articles" discloses the application of high density, wear and corrosion resistant coatings by depositing a powder composition onto a substrate by a method capable of producing a coating having an as-deposited density greater than 75 percent theoretical. The powder composition comprises two or more components; the first component consisting of 0-25 weight percent of at least one binder taken from the class consisting of cobalt, iron, nickel and alloys thereof and at least one metal carbide taken from the class consisting of tungsten, chromium, vanadium, hafnium, titanium, zirconium, niobium, molybdenum and tantalum carbides and compounds thereof; the second component consisting essentially of a single alloy or a mixture of alloys with a total composition of 6.0 to 18.0 weight percent boron, 0 to 6 weight percent silicon, 0 to 20 weight percent chromium, 0 to 5 weight percent iron and the balance nickel; the first component comprising 40 to 75 weight percent of the entire composition. The as-deposited coating is heated at a temperature greater than 950.degree. C. and for a period of time sufficient to cause substantial melting of the second component and reaction of the second component with a substantial portion of the first component. The coating is then cooled allowing the formation of borides, carbides and intermetallic phases resulting in a coating having a hardness greater than 1000 DPH.sub.300 and being virtually fully dense with no interconnected porosity.
Coatings can be produced by the hereinabove described technique using either the plasma arc spray or detonation gun (D-Gun) deposition processes.